HIT Confirm Overview

HIT CONFIRM® – HARNESSING THE POWER OF FLOW CYTOMETRY

The Emo-test HIT Confirm has been developed by Emosis to address the need of clinicians and laboratories to get access to an HIT activity test that would be readily available, on-demand, 24/7, affordable and easy to use by non-specialists.

The HIT Confirm test can be used on any flow cytometer, which are more and more available in hospitals. The new generation of smaller, cheaper benchtop flow cytometers which are easier to use by non-specialized cytometrists supports more hospitals getting access to such a powerful technology.

HIT CONFIRM® – A NEW WAY OF DEALING WITH HIT TESTING

Test principle

The Emo-test HIT Confirm® is a flow cytometry based IVD Diagnostics kit aimed at confirming that patient’s HIT antibodies are present and lead to the formation of a heparin-antibody-PF4 complex that will bind to the platelets of a donor plasma (Platelet Rich Plasma – PRP), activating them and having potentially devastating consequences for patients.

During platelet activation, changes are induced in the platelet membranes with expression of surface markers. These platelet activation markers can be studied in flow cytometry with the use of fluorescent-labeled ligand. The HIT Confirm® test uses one step only (one incubation) with two fluorophores against a marker of platelets (CD 41) and a marker of activated platelets (CD 62). After 30 minutes incubation with 2 levels of Heparin (0,3 U/mL et 100 U/mL), the proportion of relevantly activated platelets is obtained by flow cytometry (1 laser, 2 colors) counting 10,000 events.

Based on platelets obtained from a donor (for PRP), results are interpreted using a platelet activation index called HEPLA (Emosis-developed) in order to get better standardized results.

Selection of donor platelets – a challenge for all tests, less for HIT Confirm®

Selecting the right donors is of the essence and is not always easy for hospitals dealing with HIT or even other platelet tests. No international guidelines exist, this may contribute to interlaboratory variability.

Contrary to existing confirmatory tests such as SRA or HIPA, HIT Confirm® does not require washed platelets (time consuming and delicate, as it may trigger platelet activation). It requires PRP from blood donors, simply selected (donors not on medications impairing platelet function such as NSAIDs or acetylsalicylic acid, nor on Vitamin C, but also not on garlic or naturopathic medications). A safer approach to select donors could be to get preselected blood samples from Blood Transfusion Centers.

Confirmation of HITT in minutes, not days

Getting a fast answer is paramount for the clinician and the laboratory, given the potential devastating consequences for the patient possibly experiencing HIT. HIT screening tests are very sensitive but poorly specific, leading to many patients being switched to expensive and difficult to monitor alternative anticoagulants, not easy to monitor and which carry a certain bleeding risk. Existing activity tests are not easily and quickly available, results might take days or even weeks before being actionable outside of major centers.The HIT Confirm® tests takes only 30 mns to give a clear answer to the suspicion of HITT.

Ease of use – available on demand, 24/7

HIT Confirm® test can be run by a qualified laboratory technologist on a simple benchtop flow cytometer, on-demand, 24/7. It does not necessitate to batch tests requests, for cost or laboratory organization reasons. This means that the result will be very quickly available, especially when the patient is still in the hospital and can be monitored actively. In case of doubt, a test can be repeated easily if deemed necessary too.

Using microliters, not milliliters

Another benefit of using flow cytometry tests is the very low volume (in microliters) needed for the patient - this could be an advantage for specific populations, e.g. children, when compared to some platelet-based tests requiring several milliliters of blood.

Quality and better standardization

When compared to gold standard SRA, a recent abstract (results presented by Dr Tardy from Saint Etienne, France, at ISTH Congress in July 2017 *) showed an excellent outcome, with a 94% specificity (meaning very few false positives), as good as SRA, and an even better specificity (less relevant for a confirmatory test) with 90% vs. 80% for SRA.

HIT Confirm® provides therefore a much easier access to many hospitals (HITT being more prevalent in cardiology, and more and more in ECMO which is growing steadily in many countries) to much quicker HIT confirmatory results. Patient care is thus much improved, and cost burden decreased.